The present invention relates to valves for regulating fluid flow at a substantially constant and known rate and also relates to fluid piping systems employing these fluid flow regulating valves. The valve of the present invention provides a substantially constant known fluid flow of a wide range (from 0.1 to over 10,000 gallons per minute) under extreme operating parameters where the pressure differential between the upstream and downstream pressures is large (up to 20,000 psi) or small (between 1 to 100 psi).
Flow regulating valves are known in the art. For example, the valve of South African Patent No. 77/2626 comprises a valve body having a through cavity, entrance and exit apertures, and an opening with variable opening area for varying the liquid flow rate through the valve. Inside the through cavity there is a membrane that divides the cavity into two sealed compartments. A conduit is provided inside the valve body which acts as a fluid communication link between the two compartments. Fluid flow control means in the conduit operates means for varying the size of the opening. Specifically, fixed to the base of the membrane is a conical-shaped plunger that can be inserted into the opening and spring means urging the plunger away from the opening.
The South African valve, however, unlike the present invention, is not able to provide substantially constant flow under extreme operating parameters.
Also known in the art is U.S. Pat. No. 4,250,914, which discloses a valve for controlling fluid flow having a cavity divided into first and second chambers by a first membrane carrying a plunger. The plunger has one end extending into the valve outlet opening at one wall of the first chamber. A second membrane acts between an end of the plunger and a wall of the second chamber and forms a third chamber in communication with fluid at the outside of the opening through a longitudinal conduit in the plunger. Inlet fluid is supplied to the first and second chambers by a manually operable flow control valve. The plunger position is dependent upon the difference in fluid pressures in the first and second chambers and varies the size of the opening. Fluid in the third chamber counterbalances the pressure of the fluid at the outlet on the end of the plunger.
Neither the valve of U.S. Pat. No. 4,250,914 nor the valve of South African Patent No. 77/2626 teach the low torque inlet flow throttle of the present invention. This low torque throttle provides linear or non-linear flow regulation, can be easily adjusted with comparatively less force or torque, and uses a low power motor when motor driven, unlike conventional flow control throttles.
Also, neither of the above patents disclose a flow restriction point in a reference pressure passage as does the present valve. This flow restriction point minimizes "fluid packing" to allow valve responsiveness to be precisely adjusted over a wide range of flow rates despite fluctuating inlet pressures.
Also known in the art is U.S. Pat. No. 3,357,448 issued to Martin and disclosing a constant flow valve of small size. Unlike the present invention, in order to obtain constant flow the small valve of Martin requires that the effective pressure area at the top of the piston be substantially larger than the cross-sectional area of the outlet. Due to this requirement, the Martin valve is limited to a relatively small size. In contrast, the valve of the present invention may be of any size able to service a pipe having a diameter from 1/4 inch to 200 inches because it does not require that the effective pressure area at the top of the piston be much larger than the cross-sectional area of the outlet. Instead, to maintain constant flow, the effective pressure area at the top of the piston can be any size in relation to the cross-sectional area of the outlet as long as this effective pressure area at the top of the piston equals the cross-sectional area of the cylinder containing the piston less the cross-sectional area of the cylinder outlet opening.
The prior art does not show valves which modify fluid piping systems to function without balancing valves and differential pressure valves and the accompanying energy-waste due to the additional pumping pressure required by the balancing and differential pressure valves.
Furthermore, the valve of the present invention, unlike the prior art, allows the supply and return pipes of piping systems to be sized more precisely to the actual maximum flow rates encountered. Thus less fluid flow is required in a piping system using the valve of the present invention than in prior art systems. Less fluid flow results in a more energy efficient system because pump size and pump energy are functions of fluid flow volume and pressures. Specifically, one-eighth of the horse power required to circulate 1000 gallons of fluid is needed to circulate 500 gallons of fluid through the same system. On a national scale, 65 percent of the energy consumed in the United States is used to operate centrifugal or flow loads such as pumps, fans, blowers or compressors.